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sjalloq  
#1 Posted : Friday, March 13, 2009 2:15:49 AM(UTC)
sjalloq

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Hey all,

I may be being stupid here but all my Google searches are pulling up only computer heatsinks. Anyone have any idea where I can source a suitable heatsink for a Sympatico build?

Thanks, Shareef.
sjalloq  
#2 Posted : Friday, March 13, 2009 7:06:16 AM(UTC)
sjalloq

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Actually, just found this site: http://www.birminghamaluminium.com/

[Edit - deleted stupid post. Was using incorrect Vcc for my thermal calcs.]

What is Vcc on the Sympatico boards?

Edited by user Friday, March 13, 2009 7:18:49 AM(UTC)  | Reason: Not specified

rhys h  
#3 Posted : Friday, March 13, 2009 11:31:45 AM(UTC)
rhys h

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You dont need huge sinks. Look at farnell. You should be able to get somthing 200mm X 75mm for about £7.

Edited by user Friday, March 13, 2009 11:32:24 AM(UTC)  | Reason: Not specified

Brian Donegan  
#4 Posted : Friday, March 13, 2009 11:36:54 AM(UTC)
Brian Donegan

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Quote:
What is Vcc on the Sympatico boards?


That depends on the transformer(s) you use. Just multiply the transformer voltage by 1.4 for a ballpark. For example, 2x22VAC will be about +-31VDC rail voltage.
sjalloq  
#5 Posted : Friday, March 13, 2009 12:51:49 PM(UTC)
sjalloq

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OK, thanks. Can you still help me with my calcs as I want to understand. I'm using Rload as 6Ohm and Vcc = 34V.

From the LM4780 datasheet:

Pdmax(bridged) = (4*(Vcc)^2)/(2*(pi)^2*Rload) = 40.

Thermal Resistance of Sink to Air = ((150-25)-40)/40 = 2.125 C/W

Now, to me that seems much higher than any of the specs on the website I listed above. Are my numbers correct and in fact, all that the numbers show is that I don't need a very big heatsink?

Thanks.
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